This has always worked for me. Pretty much the ask? https://gist.github.com/sreekotay/08f9dfcd7553abb8f1bb17375d...
That's the first thing listed in the article? "Javascript to go fetch the HTML and insert it". What they're after is something that's _just_ HTML and not another language.
But you need a server for that to work.
That's the first thing listed in the article? "Javascript to go fetch the HTML and insert it". What they're after is something that's _just_ HTML and not another language.